Insects and diseases destroy billions of dollars worth of agricultural crops each year. Consequently, agricultural crops are sprayed with a wide range of materials, including pesticides, fertilizers, biological control agents, growth regulating compounds, and other materials that influence biological activity in and on the plant.
While the application of such materials is effective to a large degree for controlling insects and diseases of crops, it is still plagued with a variety of problems. One such problem is keeping the material from drifting from the targeted crops during the spraying operation. This is important because many of the materials are expensive and potentially harmful to humans and wildlife. Thus, by applying the material only onto the targeted crops, a more efficient, lower-cost application is achieved. It will also be less harmful to the surrounding environment.
Dusting materials, such as pesticides, are particularly difficult to contain in targeted areas, especially under windy conditions. Therefore, dusting of trees is generally avoided in favor of spraying an aqueous-based material which is easier to control under such conditions.
Attempts have been made to apply materials such as pesticides to only targeted areas. For example, an article titled, "Becoming Better Neighbors," The Grower, May 1991, pgs. 38-40, discloses an apparatus described as an "over-the-row" system. Hydraulic nozzles spray pesticides in an aqueous solution directly into trees with a hood containing the spray. Catch basins at the bottom of the apparatus catch any run-off, which is then filtered and recycled. Such an apparatus is designed for applying liquids--not dust or powders.
Most efforts to improve the efficiency of dust pesticide applications have involved the use of electrostatic forces. Briefly, this involves the placement of electrical charges (positive or negative) on the dust particles, with subsequent dependence upon an electric field (the precipitating field) to drive the particles onto the plants. Various particle-charging have been tried; e.g., friction; corona-discharge dust nozzles; and charging in the precipitating field itself. See "Electrostatic Precipitation of Pesticidal Dusts, An Outline of Research and Literature," by R. D. Brazee and W. F. Buchele, Agricultural Research Service, ARS-42-29, July 1959.
While efforts have been made in the past with varying degrees of success for containing pesticides, and the like, in only targeted areas, there still remains a need in the art for more efficient and effective methods; particularly for the application of dusts.